This invention relates to systems and methods of interconnecting optical components with passive alignment.
In order to achieve efficient and reliable transmission of optical data signals, optical components in the signal path must be aligned precisely. When aligning optical network components, there are three main elements which must be precisely aligned: the active regions of opto-electronic devices that transmit and receive the optical data signals; the optical lenses that focus and direct the optical signals; and the optical fibers that carry the focused optical data signals between the transmitters and receivers. Because optical fibers have such small dimensions, however, the alignment of these fibers with other fibers, lenses and optical devices is difficult and costly. Optical components (e.g., optical fibers, lenses, and devices) typically must be aligned with an offset error that on the order of a few microns, or less.
Efforts have been made to simplify the problem of aligning the registration elements of an optical transceiver module with the fibers of a fiber optic ribbon interconnect. In one single-fiber alignment approach, the optoelectronic device is die and wire bonded to a transceiver package so that it may be biased to its normal operating condition. The input end of the fiber is mechanically manipulated in front of the active region of the optoelectronic device until an optical coupling between the fiber and the optoelectronic device is achieved. After the optimal coupling has been achieved, the optoelectronic device is bonded in place. This process requires either human interaction or expensive equipment that automatically dithers the fiber into the optimal position. This conventional alignment process becomes significantly more complicated when applied to the coupling of arrays of optical fibers with arrays of optoelectronic devices. Additional difficulties arise when an optical lens system must be aligned between the optoelectronic devices and the optical fibers.
Still other schemes for aligning optical components have been proposed. For example, U.S. Pat. No. 5,633,968 has proposed an optical component interconnection scheme in which there are two connecting surfaces with matching surface features, and one optical component is located at a predetermined location on the first surface, and the other optical component is located at a matching location on the second surface. When the two surfaces are mated in a face-to-face fashion, they are locked into a stable position through the matched surface features. The first and the second optical components are aligned properly as they are located at a same spot with respect to the face-locking surface features. The unique surface features and the locations of the optical components may be registered by a lithographic method that has sub-micron accuracy.
The invention features a system for interconnecting a first optical component and a second optical component in which the first optical component is guided passively into precise alignment with the second optical component. The passive alignment system of the invention may be used with a wide variety of different optical connectors, including connectors implemented in accordance with existing optical connection standards, without the need for proprietary interlocking features or special modification.
In one aspect, the invention features a system for interconnecting a first optical component and a second optical component in alignment with respect to a common optical axis. The system comprises a base and a guide structure. The base has a first surface exposed for contact with a front surface of the first optical component and a second surface configured to contact a front surface of the second optical component, and defines a transparent optical aperture extending from the first base surface to the second base surface and aligned with respect to the optical axis. The guide structure is supported by the base in fixed registration with respect to the optical axis and is exposed for contact with an exposed peripheral surface of the first optical component at three or more spaced apart discrete locations.
Embodiments in accordance with this aspect of the invention may include one or more of the following features.
The guide structure preferably is exposed for contact with the exposed peripheral surface of the first optical component at locations axially displaced from the first base surface. The guide structure may be exposed for contact with the exposed peripheral surface of the first optical component at locations concentrically circumscribing the optical axis. The guide structure preferably is configured to guide the first optical component into alignment with the optical axis with a transverse offset on the order of 4 microns or less.
In some embodiments, the guide structure comprises a set of three or more alignment elements secured to the base. The alignment elements may be substantially spherical in shape. In some embodiments, the alignment elements are bonded to the base (e.g., by anodic bonding). In other embodiments, the alignment elements are secured to the base by a retainer. The base may comprise a set of positioning cavities in the front base surface constructed to laterally restrain the alignment elements in fixed registration with respect to the optical axis. The positioning cavities may be characterized by sloped sidewalls. The positioning cavities may be defined photolithographically. For example, the positioning cavities may have surfaces corresponding to (111) planes anisotropically etched into a silicon substrate.
In some embodiments, the second optical component comprises an optical lens system secured to the base in fixed registration with respect to the optical axis. In other embodiments, the optical lens system is integrated into the base. The second optical component preferably further comprises an optical device system secured in fixed registration with respect to the optical axis. The second optical component may further comprise a spacer substrate secured between the optical lens system and the optical device system.
In another aspect, the invention features a method of fabricating the above-described optical component interconnection system.
Other features and advantages of the invention will become apparent from the following description, including the drawings and the claims.